The present invention relates to a differential scanning calorimeter for a thermal analyzer.
A differential scanning calorimeter of a thermal analyzer is equipped with a heat-controlled heat sink, a sample within the heat sink, a reference material holder, a heater for heating the heat sink, and a cooling device for cooling the heat sink. With differential scanning calorimeters of the related art, a cooling device comes into direct contact with a heat sink so as to cool the heat sink. Cooling devices taking liquid nitrogen as a medium are disclosed in Japanese issued Patent Tokkohei 2-116744 and Japanese issued Patent Tokkohei 7-122619. At the cooling device, an electrical cooling device that compresses a cooling agent using a compressor so as to cause adiabatic expansion that in turn produces cooling is provided. A metallic member connected to the electrical cooling device then makes direct contact with a heat sink so as to cause cooling.
With heat-flux differential scanning calorimeters of the related art, it is preferable for providing power to the heater that heats the heat sink to be of high-resolution in order to control the temperature of the heat sink as precisely as possible. For example, with differential scanning calorimeters with an upper limit of 750° C., an ideal maximum heater power is taken to be a value sufficient for requiring heating necessary to bring the heat sink temperature up to 750° C.
Differential scanning calorimeters are connected to a device for cooling a heatsink such as an electrical cooling device that compresses a cooling medium using, for example, a compressor so as to bring about adiabatic expansion which in turn brings about cooling in order to measure negative temperature bands or measure falling temperatures. However, with differential scanning calorimeters designed with the sufficient heating power necessary for heating processing, in cases where a cooling device is not connected, it is possible for the temperature to be increased up to 750° C. but when an electrical cooling device is connected, the current for heating the heat sink flows in the cooling mechanism, and because extra heater power is therefore required, heating up to 750° C. cannot be achieved for the differential scanning calorimeter and the temperature range that can be measured is therefore reduced. Further, when a cooling device is installed and the outputted heater power is increased to achieve heating up to 750° C., the resolution of the control of the heater power deteriorates, and heat sink temperature can no longer be controlled in a precise manner.
In order to resolve the aforementioned problems, the current application sets out to precisely control heat sink temperature using high-resolution heater power without reducing the measurable temperature range of a differential scanning calorimeter to which an electrical cooling device for cooling a heat sink is connected.